Intumescent, coated roofing granules and asphalt composition felt-base roofing containing the same



Jan. 23,1968

. C. E. HINDS INTUMESCENT, COATED ROOFING GRANULES AND ASPHALT COMPOSITION FELT-BASE ROOFING CONTAINING THE SAME Filed April 28, 1964 United States Patent C) 3,365,322 INTUMESCENT, COATED ROOFING GRANULES AND ASPHALT COMPOSITION FELT BASE RGQFING CONTAINING THE SAME Caryl E. Hinds, Norwood, Mass., assignor to Bird & Son, Inc., East Walpole, Mass, a corporation of Massachusetts Filed Apr. 28, 1964, Ser. No. 363,171 6 Claims. (Cl. 117-30) ABSTRACT OF THE DISCLOSURE A fire retardant asphalt composition felt-base roofing material comprising a layer of asphalt-saturated roofing felt having on one face thereof at least two layers of asphaltic composition and, between said layers, an intermediate layer of refractory mineral roofing granules in dividually coated with a reaction product of a boraxsodium silicate mixture which upon exposure of the roofing and coated granules to flame temperatures intumesces to convert said intermediate layer to a hard tough insulating crust; and, as an article of commerce, such coated granules per se.

This invention relates to fire-retardant roofing and particularly to fire-retardant asphalt shingles or roll roofing. It is further concerned with an intumescing-coated granule interlayer useful in producing these roofing materials and with the method of making roofing incorporating such a coated granule layer.

Roofing and shingle compositions of the conventional type consist of an asphalt-saturated felt base coated with one or more layers of asphalt which may or may not contain added mineral reinforcing fillers of the nature of slate or rock dust or the like, and have mineral granules embedded in the upper portions of the asphalt coating. These roofings, although fire-resistant, are combustible and when exposed to conditions of severe fire will ignite with subsequent softening and flowing of the asphalt coatings, thus tending to further the spread of flame.

The art has attempted to overcome the defects inherent in such conventional roofings and efforts have been made to contain the flow of the coating by means of fillers such as asbestos, fibrous filler materials or the like, or of minerals such as vermiculite which will expand on heating. However, the quantities of these materials which when incorporated in asphalt coatings will adequately prevent excessive flow of the coating and also provide a suitable barrier to prevent fire from reaching the underlying roof deck are so excessive that the viscosity of the resulting asphalt coating is such that it is difficult and well nigh impossible to apply the asphalt coatings by means of standard coating equipment.

In the Donegan patent, No. 2,782,129, there is used an interlayer of unexpanded vermiculite between two layers of an asphaltic composition on an asphalt-saturated felt base. Such use of vermiculite introduces at least two disadvantages. First of all, it is costly, and, secondly, the low specific gravity of vermiculite makes it difficult in plant practice to properly proportion the various materials used in manufacturing the roofing, particularly where a weight per unit area (e.g. per square of roofing) is a factor in a roofing specification.

It is an object of this invention to provide an asphaltcoated and asphalt-saturated felt base roofing which can be made in conventional manner on standard machine equipment and which will have the requisite fire-retardant qualities to pass the Underwriters Laboratories tests for Class A roofing.

It is another object to provide a fire-retardant roofing having top surface coatings which upon exposure to flame will not freely run or drip and thus will not further spread the flame.

A further object is to provide a fire-retardant roofing, the upper surface coatings of which on exposure to flame will intumesce and form a cokeor char which will not break up but will remain in place and not be displaced from its original position, thereby hindering the flame from reaching the roof deck and causing its ignition.

A further object is to provide a roofing material which by intumescence in the upper series of coatings will tend to increase the insulation of a flame from an underlying wooden deck.

A further object is to provide a roofing having an upper coating which upon exposure to flame will form an insulating mass or crust which is sulficiently cohesive and resistant to thermal stresses to maintain an effective insulating barrier to prevent flame from reaching an underlying roof deck.

A further object is to provide an improved method of manufacturing such roofing.

A still further object of the invention is to provide intumescing-coated refractory granules which will serve as an effective fire-retarding interlayer in the manufacture of the roofing described.

Other and further objects, features and advantages of the invention will become apparent from the following description of illustrative embodiments of and ways of practicing the invention, in which description reference is made to the accompanying drawing, in which FIG. 1 is a perspective view of a roofing shingle in accordance with the invention, partly broken away to illustrate its construction;

FIG. 2 is a cross sectional view of the shingle of FIG. 1, to an enlarged scale; and,

FIG. 3 is a diagrammatic illustration of the method of making the shingle of FIG. 1.

The foregoing and other objects of the invention are accomplished by use between a sheet of asphalt impregnated roofing felt and a top layer of decorative granules of an interlayer of intumescing-coated mineral granules positioned between two layers of an asphalt coating composition comprising asphalt and fine mineral matter such as slate or rock dust. The upper layer of asphalt coating composition, i.e., the layer nearest said top layer preferably also contains between about 5% and about 20% by weight of the asphalt coating composition of asbestos fibre of a class equivalent to Group 7 grade. Group 7 grade as used herein refers to a type so classified accordting to a screen analysis as shown in Canadian Dept. of Mines Bulletin #707 (1931) and U.S. Bureau of Mines Bulletin #403-Asbestos (1937). The other layer of asphalt coating composition also may contain such asbestos fiber, in the same amount.

In the preparation of my fire-retardant roofing, referring to the drawing and first to FIG. 3, a sheet of a roofing felt, e.g., a conventional organic fiber roofing felt 2, as for example one having a thickness in the range .055 to .070 inch and weighing about 50 to 60 pounds per 3 480 sq. ft. of dry felt, is impregnated with asphalt at 4 to about 175185% of its dry weight in a manner well known in the art.

To the top face of the so impregnated sheet there is applied a first or lower layer of asphalt coating composition 6 comprising asphalt and mineral reinforcing matter including asbestos fibre of the class and in the amounts above described. Although I have found that by use of my intumescing-coated granules in the interlayer it is not essential to have any asbestos fibre in this lower layer in order to retain freedom from undesirable flow of the ignited coating, it is somewhat preferable to have about 5% to about 20% by weight of the asphalt coating composition of asbestos fiber, so that the coke or char mass will possess good cohesive strength and not break up into smaller pieces. The amount of asphalt coating composition s0 applied and which has a softening point about 250-285 F. will preferably be about 20 pounds per 100 sq. ft. or may vary, for example, between about 8 pounds and about 30 pounds per 100 sq. ft.

The back face of the felt 2 optionally may also be coated with this same coating composition, or with an asphalt coating composition which contains no asbestos fibre, and then lightly coated with talc, soapstone or the like.

After the coating 6 has been smoothed to the desired thickness, it is surfaced with a layer 8 of my intumescingcoated granules consisting of mineral granules 10 having coatings 12 of a material which intumesces when heated, as hereinafter described.

After pressing the resulting composite at 14 to embed the granules, any excess granules are removed and a second or upper layer 16 of asphalt coating composition Similar in composition and amount to the lower layer 6 is applied and smoothed to the desired thickness. It is highly desirable that the asbestos fiber be included in this upper layer, as is indicated at 18.

A top layer 20 of protective and decorative mineral granules is then applied in conventional manner and amount and the sheet cooled and cut into strips, shingles or the like.

When the roofing of the invention is exposed to the heat of a fiame, as for example in the tests prescribed by the Underwriters Laboratories for determination of Class A qualification, the coating 12 on the granules 10 of the interlayer 8 intumesces and, increasing in volume several fold, swells into a porous mass which tends to prevent flowing and running of the asphalt under the heat of the flame. The granule coating 12 first intumesces to a porous mass which, along with the asphalt and granules 10, will upon continuous heating fuse or sinter into a crust or coked mass that tends to insulate the roof deck from the flame. The intumescence of the coating takes place over all surfaces of the granules in the interlayer 8 and there is an increase in volume of the composite coatings and granule layers which on formation of the porous coked mass increases the vertical distance between the roof deck and the flame, e.g., of a burning brand resting on the roofing surface. As further heating occurs, there takes place a shrinkage of the coating on the granules and at least a partial sintering of the intumesced coating which combines with the other materials in the char. The granules of the interlayer, individually coated with intumescing material, produce upon heating an absorbent intumesced mass which prevents sliding and easy ignition of the asphalt coating. The solid glasslike material formed on increased heating fuses or sinters with the granules and coked asphalt to form a hard, tough insulating crust which acts as a firewall to protect the roof deck from ignition temperatures. The presence of the granules is thus highly advantageous. This intumescing granule coating, which is low in cost, requires no manufacturing equipment or operations beyond well known normal methods for coating of roofing granules.

Although the use of my intumescing-coated granules will prevent the undesirable flow or running of the asphalt coatings and will provide a coked mass which will be fire-retardant per se, it is desirable that some amount of asbestos fibre 18 of proper length be present in the upper layer 16. As the organic matter in the mass burns out, the mass becomes weak and tends to crumble. The presence of the asbestos fibre helps to tie the coked mass together through interlocking of the asbestos fibers.

I find that asbestos of the Group 7 grade is most desirable because of its fiber length. Coarser grades having fibers of longer length are too coarse and, when used in amounts sufiicient to obtain the desired degree of strength in the ignited coke or char mass, make for difficulty in application of asphalt coating by conventional equipment. Use of fibers shorter than Group 7 grade will lessen flow stability, and, furthermore, these fibers lack the intermeshing quality required to maintain a stable coke or char mass upon ignition of the bituminous coating.

The mineral filler such as rock dust in the asphalt coating composition is used principally to reinforce this coating and also reinforce the coked crust. The asphalt compositions used may contain up to 50% by Weight of total asbestos fibre and such mineral filler and yet be suitable for application by commonly known means.

As base granules 10 for preparation of the intumescingcoated granules, I may use any mineral granule suitable for use in roofing, in gradings which will pass 4 mesh and be retained on mesh. Typically I may use a suitable rock which will withstand breaking up or shattering at the temperatures encountered in the Underwriters Laboratories tests for qualification of Class A roofing. I prefer to use granules of the grading commonly known as #11. This grading is substantially as follows:

Minimum I Standard Maximum Retained on 8 mesh screen, i

percent by weight 0.0 0.0 0.0 Retained on 10 mesh screen,

percent by weight 0.0 1.0 2.0 Retained on 14 mesh screen,

percent by weight 30.0 35. O 40. 0 Retained on 20 mesh screen,

percent by weight 30. 0 37. 0 44. 0 Retained on 28 mesh screen,

percent by weight 15. 0 20.0 25. 0 Retained on 35 mesh screen,

percent by weight 3.0 G. 0 9. 0 Pass 35 mesh screen, p

weight 0. 0 1. 0 2. 0

When made on the above base grading, I prefer to use about 25 pounds of intumescing-coated granules per 100 sq. ft. of roofing, but any amount within the limits 20 pounds to 30 pounds per 100 sq. ft. will provide the protection required.

It is possible, although not preferable, to use as base granules 10 a grading commonly known as #9 and which is substantially as follows:

Minimum Standard Maximum Retained on 4 mesh screen,

percent by weight. 0. 0 0.0 0.0 Retained on 6 mesh 5 con,

percent by weight 0 0 0. 5 1.0 Retained on 8 mesh screen,

percent by weight 1i). 0 22. 0 25.0 Retained on 10 mesh screen,

percent by weight 38. 0 42. 0 46. 0 Retained on 14 mesh screen,

percent by weight 23.0 27.0 31. 0 Retained on 20 mesh screen,

percent by weight 5. 0 7.0 9. 0 Retained on 28 mesh screen,

percent by weight 0. 0 1.0 2. 0 Pass 28 mesh screen, percent by weight 0. 0 0. 5 l. 0

Using this as base I would use about 44 pounds of intumescingcoated granules per 100 sq. ft., but any amount within the range 40 pounds to 50 pounds is satisfactory.

It is also possible, although again not preferable, to use as the base granules 10 a grading finer than #11 and commonly known as #18 grading. This grading is substantially as follows:

Minimum Standard Maximum Retained on 10 mesh screen,

percent by weight 0. O 0. 0. Retained on 14 mesh screen,

percent by weight 0. 0 0. 5 l. 0 Retained on 20 mesh screen,

percent by weight 0. 5 2.0 3.0 Retained on 28 mesh screen,

percent by weight 22.0 27.0 31. 0 Retained on 35 mesh screen,

percent by weight 28. 0 3S. 0 43. 0 Retained on 65 mesh screen,

percent by weight 25.0 28.0 32. O Retained on 100 mesh screen,

percent by weight 0. 5 3. 0 5. 0 Pass 100 mesh screen, percent by weight 0.0 1. 5 3.0

With this grading as the base, I would use about pounds of intumescing-coated granules per 100 sq. ft. of roofing, but any amount within the range 8 pounds to pounds is satisfactory.

The interlayer 8 may be composed entirely of intumescing-coated granules or there may be mixed therewith other mineral granules or the like, so long as there is used a sufficient quantity of the intumes-cing-coated granules, and coming within the limits set forth above for the respective grades, to impart the necessary fire-retardance required in the complete roofing material.

It is desirable that the intumescing coating 12 be of such a nature that iutumescence may take place readily and rapidly at temperatures sufliciently low that this action will occur before the asphalt of the bituminous coatings has become decomposed and'charred and lost its binding effect. It must likewise occur before the asphalt has gradually hardened to the point where it resists the expansion of the intumescing coating and results in inability of the intumescing coating to intermix with the coked asphalt binder and other materials to form a firm insulating mass.

A preferred typical formula for an intumescing coating 12 to be applied to a mineral granule base 10 is as follows. Throughout this application, parts are by weight unless otherwise stated.

100 parts by weight base granules (#11 grading) 4 parts by weight borax (5 mol) 4 parts by weight G brand sodium silicate powder 4 parts by weight N brand sodium silicate solution 2 parts by Weight water G brand sodium silicate is a powdered sodium silicate, supplied by Philadelphia Quartz 00., having a Na O to SiO ratio of 1:322.

N brand sodium silicate is a sodium silicate solution, supplied by Philadelphia Quartz 00., containing 37.6% solids having a Na O to SiO ratio of 13.22. The granules are coated as follows. The borax and G brand sodium silicate are added to the granules in a suitable mixing drum or the like and the mixture tumbled for about 2 minutes to mix the dry ingredients. The water is added and the mixing continued for an added 4 minutes. The N brand sodium silicate is then added and the mixing continued for another 8 minues. The coated granules are then dried with mild agitation at about 220-250 F. They are then cooled to about 100 F. and are preferably treated with slate treating oil (a very light mineral oil) containing a moisture repellent at about 10 pounds per ton of granules. The moisture repellent prevents absorption of moisture by the coating and sticking in storage. The slate treating oil aids in the embedding of the granules in asphalt.

The borax may be used in the form of sodium tetraborate pentahydrate (5 mol); sodium tetraborate decahydrate (10 mol) or sodium borate concentrates (Rasorite) passing 10 mesh to passing 200 mesh. The soluble sodium silicate solution in liquid form may have a ratio of sodium oxide to silica from 1:1.6 to 113.75. The soluble silicaie in powder form may be any which passes 20 mesh to 200 mesh and has a sodium oxide to silica ratio of from 2:1 to 1:322.

Broadly, in the manufacture of the intumescing-coated granules, and depending of course upon the screen grading of the base granule used, there may be used, for each parts by weight of the mineral granule base, from 1 to 50 parts by weight of borax, with the other ingredients proportioned thereto as in the above formula.

Preferred compositions are those variations of the above formula falling within the limits of 1 to 7 parts by weight of borax; 0 to 6 parts by weight of G brand sodium silicate; 3 to 10 parts by weight of N brand sodium silicate, and 1 to 5 parts, by weight, of water.

As to the slate treating oil, to provide protective coatings to prevent water absorption by the intumescingcoated granules and likewise to aid embedding of the granules in asphalt, there may be used as coatings on the granules any of the following materials: asphalt emulsions, oils, silicones or latex emulsions.

The intumescing coating 12, and/or the bituminous coatings 6 and 16 may contain supplementary additives, as is known in the art, and the completed roofing material may include additional layers or materials than those described.

I claim:

1. A fire-retardant roofing material comprising a sheet of a roofing felt impregnated with an asphaltic material, a lower coating layer of an asphaltic composition on one face of said felt, an interlayer of refractory mineral roofing granules adhered to said lower coating layer, said granules being individually coated with a surface coating comprising a reaction product of a sodium silicate and borax which intumesces upon exposure of the coated granules to flame temperatures, an upper coating layer of an asphaltic composition over and adhered to said mineral granule layer, and a layer of decorative mineral granules adhering to said upper asphaltic composition layer.

2. The roofing material of claim 1 wherein said upper asphaltic composition layer includes asbestos fibre.

3. The roofing material of claim 1 wherein said reac tion product is a reaction product of l to 50 parts by weight of borax for each 100 parts by weight of uncoated mineral granules.

4. The roofing material of claim 3 wherein said reaction product is a reaction product of 1 to 7 parts by weight of borax for each 100 parts by weight of uncoated mineral granules.

5. The roofing material of claim 2 wherein said reaction product is a reaction product of 1 to 50 parts by weight of borax for each 100 parts by weight of uncoated mineral granules.

6. The roofing material of claim 5 wherein said reaction product is a reaction product of 1 to 7 parts by weight of borax for each 100 parts by weight of uncoated mineral granules.

References Cited UNITED STATES PATENTS 917,543 4/1909 Cohen 161-205 1,271,506 7/1918 Ferguson 117-138 1,548,910 8/1925 Sherman 161-205 1,642,316 9/1927 Wardell 161-210 1,766,814 6/1930 Fisher 117-100 2,139,955 12/1938 Hillers et al 117-100 2,782,129 2/1957 Donegan 117-30 3,053,714 9/1962 Edwards 1 61-238 3,090,764 5/1963 Ellis et al 260-285 WILLIAM D. MARTIN, Primary Examiner. MURRAY KATZ, Examiner. T. G, QAYIS, Assistant Examiner. 

